Grain dryer

ABSTRACT

A GRAIN DYE IS DISCLOSED IN WHICH THERE ARE OF ANGULARLY-DISPOSED SHELVES, ONE ABOVE THE OTHER, PROVIDING GRAIN BEDS WHICH ARE INCLINED TOWARD COMMON INTERMEDIATE DISCHARGE COLUMNS, THERE BEING A HOT AIR DUCT EXTENDING HORIZONTALLY ALONG THE UPPER EDGE OF EACH SHELF FROM WHICH HOT AIR AT RELATIVELY HIGH TEMPERATURE IS DIRECTED DOWNWARDLY AT HIGH VELOCITY AND PRESSURE, IN CONCURRENT FLOW THROUGH THE BED OF GRAIN SUPPORTED ON THE SHELF, AND THERE BEING COMMON MEANS FOR FEEDING GRAIN TO THE UPPER EDGES OF ALL OF THE SHELVES TO MAINTAIN THE INCLINED BEDS FILLED. METERING MEANS AT THE LOWER EDGE OF EACH SHELF PROVIDES FOR METERING FROM EACH SHELF A PREDETERMINED RATE. THE FEED OF GRAIN INTO THE DRYER IS AUTOMATICALLY CONTROLLED TO MAINTAIN A PREDETERMINED LEVEL. AN OPTIONALLY USABLE COOLER IS ALSO DISCLOSED WHICH MAY BE LOCATED BELOW THE DRYING UNIT AND WHICH IS ADAPTED TO DELIVER COOLING AIR UPWARDLY IN COUNTERFLOW WITH RESPECT TO THE FALLING GRAIN.

Jan. 12, 1971 McKENZ|E ET AL GRAIN DRYER Fild June 25, 1969 5Sheets-Sheet l |NVENTORS GERALD L. ZACHARIAH BRUCE A. M: KENZIE ROBERTM. PEART RAYMOND R. OHLGREN ATTORNEYS Jan. 12, 1971 B McK N E ET AL3,553,846

GRAIN DRYER Filed June 25, 1969 5Sheets-Sheet 2 INVENTORS GERALD L.ZACHARIAH BRUCE A. Me KENZIE ROBERT M. PEART RAYMOND FLOHLGREN ATTORNEYSs. A. MCKENZIE ET AL 3,553,846

GRAIN DRYER Jan. 12, 1971 5 Sheets-Sheet 5 Filed Jdne 25, 1969 INVENTORSGERALDL. ZACHARIAH BRUCE A. Mr: KENZIE ROBERT M. PEART RAYMOND R.OHLGREN BY W ATTORNEYS Jan. 12, 1971 McKENZ|E ETAL 3,553,846

GRAIN DRYER I Filed June 25, 1969 5 Sheets-Sheet i INVENTORS GERALD L.ZACHARIAH BRUCE A, MC KENZIE -ROBERT M.PEART RAYMOND R. OHLGRE'NATTORNEYS Jan. 12, 1971 B. A.

med June 25, 11969 MCKENZIE T T 3,553,846

GRAIN DRYER I 5 Sheets-Sheet INVE NTORS GERALD L. ZACHARIAH BRUCE A. M:KENZIE ROBERT M. PEART RAYMOND R.OHLGREN ATTORNEYS United States Patent3,553,846 7 GRAIN DRYER Bruce A. McKenzie, Lafayette, and Gerald L.Zachariah and Robert M. Peait, West Lafayette, Ind., and Raymond R.Ohlgren, Pewaukee, Wis., assignors to The Heil Co., Milwaukee, Wis., acorporation of Wisconsin Filed June 25, 1969, Ser. No. 836,387 Int. Cl.F26b 13/10 US. CI. 34-56 18 Claims ABSTRACT OF THE DISCLOSURE A graindye is disclosed in which there are tiers of angularly-disposed shelves,one above the other, providing grain beds which are inclined towardcommon intermediate discharge columns, there being a hot air ductextending horizontally along the upper edge of each shelf from which hotair at relatively high temperature is directed downwardly at highvelocity and pressure, in concurrent flow through the bed of grainsupported on the shelf, and there being common means for feeding grainto the upper edges of all of the shelves to maintain the inclined bedsfilled. Metering means at the lower edge of each shelf provides formetering from each shelf a predetermined rate. The feed of grain intothe dryer is antomatically controlled to maintain a predetermined level.An optionally usable cooler is also disclosed which may be located belowthe drying unit and which is adapted to deliver cooling air upwardly incounterflow with respect to the falling grain.

BACKGROUND OF THE INVENTION Field of the invention The present inventionis particularly adapted for the drying of corn, but is suitable for usein the drying of other grains or granular materials.

Description of the prior art In the most commonly used grain dryers thegrain is permitted to descend by gravity in a column, flowing downwardlyover and on both sides of horizontally-disposed hot air ducts, or elsehot air is directed in cross flow through the colmun. One such anarrangement is described in Randoplh Pat. No. 1,239,216 where the entirestack is filled with vertical and horizontal rows of air ducts, each ofwhich is surrounded by the grain. In other types of constructions theair ducts of the general type disclosed in the Randolph patent areinverted Vs in cross section and open on the underside. Another type ofdryer which is common in the prior art makes use of oppositely-directeddownwardly-inclined shelves in a zig-zag arrangement, one shelfdischarging from above into an oppositely-directed shelf below. In allof these prior devices, if the drying air is at too high a temperature,there will be damage to the grain. Therefore, in these prior devices,relatively low temperature air is used (about 230 F.) and the grain issubjected to the drying air for a relatively long period of time. Thusthe installations must belarge 3,553,846 Patented Jan. 12, 1971 iceSUMMARY OF THE INVENTION The present invention provides, in-a graindryer, at least one tier of inclined shelves providing spacing forinclined beds which are kept filled with grain introducedfrom above.There is means at the lower end of each shelf for metering grain fromthe bed at a predetermined rate and there is a horizontally-disposed airduct at the upper end of each shelf over which the entering grain moves,each air duct being equipped to discharge air in concurrent flow at highvelocity and pressure through each bed of grain, in a manner providingfor fast and uniform drying without damage to the grain. The feed ofgrain into the dryer is automatically controlled to maintain apredetermined level. In addition, there is optional means, preferablylocated below the drying unit, which is capable of directing cooling airupwardly through the falling grain in counter flow.

One of the objects of the invention is to provide for eificient dryingof grain by the use of high velocity, high pressure air at a relativelyhigh temperature.

A further object of the invention is to provide a grain dryer by whichmore grain can be handled over the same flow space than dryersheretofore proposed.

A further object of the invention is to provide a grain dryer in whichall particles of the grain are subjected to substantially the sameamount of heat for substantially the same lengthof time.

A further object of the invention is to provide a grain dryer which isrelatively simple in design and construction, reliable in operation,relatively small in size for its capacity, and otherwise well adaptedfor the purposes described.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, in which the samereference numerals designate the same or similar parts in all of theviews:

FIG. 1 is a front elevational view of the improved grain dryer, parts ofthe casing being broken away to show the interior;

FIG. 2 is an end view thereof with the lower portion of the casingbroken away;

FIG. 3 is a vertical sectional view through the dryer portion of thedevice'taken approximately on the line 33 of FIG. 1; a

FIG. 4 is a vertical sectional view taken approximately on the line 44of FIG. 1;

FIG. 5 is a view looking at the top of one of the hot air ducts takenapproximately on the line 5-5 of FIG. 3, parts being broken away andshown in section;

FIG. 6 is a horizontal sectional view through the lower portion of thedevice showing the blowers and air ducts in plan view;

FIG. 7 is a vertical sectional view through the cooling unit; I

FIG. 8 is a sectional view taken on the line 8-8 of FIG. 7;

for the motors which operate the feed augers;

FIG. is a diagrammatic view of the emergency level control;

FIG. 11 is a diagrammatic view illustrating the drive for the grainmetering wheels; and

FIG. 12 is a diagrammatic view showing the control circuit for thosemetering wheels which control the discharge from the cooler.

Referring more particularly to the drawings, the numetal designates aninlet passageway for grain. Any suitable means may be employed forfeeding grain into the dryer. In the illustrated example the grain isdirected onto the ends of augers 21 and 22. The auger 21 operates in anauger housing 23 which is located over the plenum chamber only, therebeing no auger housing for the rest of the length of the auger, and theauger 22 in a similar auger housing 24. Grain is thus directed in twodirections by the augers and is discharged from the open bottomed augersinto the dryer sections 25, one on each side, to flow by gravity downthe oppositely-inclined walls 26 (see FIG. 3) of an interior casing 27having a top dividing ridge 28.

Each auger may be driven through an endless drive belt or chain 82 (seeFIGS. 1 and 4) driven by an electric motor 83. When the grain on theright hand side of FIG. 1 is filled to a proper level this is sensed bythe level detector 84 which automatically opens a switch 85 to theelectric motor 83 for the particular side, stopping the motor and auger(see FIG. 9). A similar action takes place on the other side where thedetector 86 causes opening of a switch 87 to the other electric motor 83to stop the operation of the auger on this side. When the level of thegrain drops below the detectors 84 and 86 the augers will againautomatically operate to replenish the grain.

As an extra precaution there may be emergency indictator fingers 88 and89 on the two sides, as shown in FIG. 1. Referring now to FIG. 10,should the grain level fall below the emergency detector fingers 88 or89, said fingers will be released as shown in the full line position ofFIG. 10, causing closing of a microswitch 90 and operation of a horn 91or other signal which will warn the operator that the level controls 84and 86 have not been operating properly, and that the level has fallento a dangerous point.

The lower edges of the inclined walls 26 are connected as at 30 to theupper edges of walls 29 which diverge outwardly from the upper end ofthe discharge column 49. Spaced below each of the inclined walls 29 is atier of inclined shelves 31 for supporting beds of grain to be dried.Inasmuch as the construction on the two sides of the plenum chamber isthe same, only one will be described. At the upper edge of each shelf 31is a hot air duct 32. Each hot air duct is constructed as shown in FIG.5 to provide a downwardly-inclined top wall 33, a back wall 34, and abottom wall 35. As one way of providing for efiicient discharge of thisair, within each duct is an angularly-extending partition 36, one end ofwhich meets the back wall 34 at one end of the air duct, and the otherend of which meets the forward edge of the top wall 33 at the other endof the duct. Another angular partition 37 extending at the same angle asthe partition 36 has one end starting midway of the width of the airduct as at 38 at the inlet end of the duct, and has its other endterminating midway of the length of the duct adjacent the forwardportion thereof, as at 39. With this arrangement, part of the airintroduced into the inlet end 40 will flow through a passageway 41located between the partitions 36 and 37, and the remainder will flowthrough a passageway 42 located in front of the partition 37'. Thepassageway 42 is in open communication with a bed of grain supported onone of the inclined shelves 31 and filling the space between said shelfand the wall thereabove. The passageway 41 is in communicationthroughout the latter half of its length with the bed of grain. Withthis arrangement the air entering each duct at the end 40 is welldistributed so that it is discharged from all portions of the length ofeach duct. Other means of providing even air distribution may beemployed. There is preferably insulation 43 over and under thepassageway 41 and insulation 44 over and under the passageway 42. Thusgrain entering a column and initially supported on top of a hot air ductwill not be scorched. The lowermost hot air duct on each side isconnected by a deflector sheet 45 with the adjacent wall so that nograin can pass downwardly below the lowermost shelf.

In the drying of com the preferred angle for the shelf is 51 from thehorizontal. The angle, however, may be anywhere between the lowest anglewhich will produce a flow of the grain, about 40, and 60. In a typicalcorn installation each shelf 31 may be 8 feet long and the spacing W(FIG. 3) between ach pair of shelves may be as much as 15 inches. Themean depth D (FIG. 3) of each bed of grain is 3 feet. The ratio W/D maybe anywhere between 1/1.5 to 1/8. Each hot air duct 32 is approximately8 inches wide and 8 feet long, and the clearance between the top wall 33of each duct and the angular wall thereabove is approximately 4 inchesand as small as possible without impeding the flow of grain. It ispreferred to have the ratio A/ W anywhere between 1/2 to 9/ 10, where Ais the height of a duct as shown in FIG. 3. For corn a ratio of 2/ 3 isvery satisfactory. It is to be noted that each hot air duct has a deadair space 46 providing insulation for the back wall 34. Thus any grainin contact with the back wall 34 will not become scorched. The angle ofthe shelves provides for gravity feed toward the metering wheels 48 butprevents too dense compacting of the bed of grain on each shelf. If thecolumn of grain were vertical it would be packed so densely that anobjectionably high air pressure might be required to move air throughit.

At the lower end of each shelf is a closure plate 47 which terminatesshort of the lower edge of each shelf 31. Each plate is perforated byholes of a size to release air but not grain. This leaves space withinwhich a rotary metering paddle wheel 48 may be accommodated. Between thetiers on the two sides of FIG. 3 is a vertical discharge space 49 openat the lower end as at 50. The metering Wheels 48 may all be driven by avariable speed D.C. electric motor 92 (see FIG. 11) which through anendless chain drive 93 drives the sprockets of the metering valves 48 inthe directions indicated in FIG. 11 to discharge grain into the centralcolumn 49. Heated air under pressure is forced through the ambienttemperature grain supported on the tiers 31 into the central chamber 49,

i as will be hereinafter described. Due to the inclines of the tiers 31the grain flows by gravity through the inclined drying chambers at arate determined by the rotational speed of the metering paddle wheels48.

Between the two sides of the dryer, i.e. the side fed by the auger 23,and the side fed by the auger 24, is a plenum area 51 which isillustrated in FIG. 4, the construction on the two sides of the plenumbeing the same. Extending upwardly within the plenum area are verticalplenum ducts 52 through which hot air is delivered, as will behereinafter pointed out. Each duct 52 communicates with openings 53 ineach of the walls of the plenum area, each opening 53 being inregistration with the intake end 40 of one of the hot air ducts 32.

THE COOLER The cooler is designated generally by the numeral 54 (seeFIGS. 2 and 7), and may fit below each dryer section, each coolercomprising two sections, one below the portion of the dryer fed by theauger 23 and the other below the portion of the dryer fed by the auger24. If desired, the cooler may be omitted and the grain cooled by anyconventional means. Grain discharged through the opening 50 of FIG. 3 ofeach dryer section is divided by inclined walls 55 of a suction duct 56which extends lengthwise of each cooler section. The inclined walls 55are spaced a short distance below wall portions 55 to providepassageways 116 therebetween, of limited height, through which the grainslowly descends, the grain maintaining said passageways substantiallysealed against the inflow of exhaust air from the dryer section into thecooling section below. Below the duct 56 are open-bottomed cooling airpassageways 57. Grain descendingfrom the sides .55 of the duct 56 isdistributed to fall on top of the air cooling ducts 57 and on top of thedownwardly-inclined baflles 58. Below. the central air duct 57 is aninverted V-shaped guide 59 having inclined walls 60. Grain from thesewalls is intercepted by inclined baffles 61 and the grain is ultimatelydischarged through spaces 62 and 63 onto an endless discharge conveyor64, which, conveyor extends the entire length of the dryer of FIG. 1 andconveys the dried grain to a point of discharge, as is clear from FIG.1.

The discharge from the spaces 62 and 63 iscontrolled may be located inthe passageways 62 and 63 or in any other location, and which are drivenbyan electric motor 96. The motor on each side for driving the dischargewheels 62 and 63' is under the control of a level detector 97 positionedin the feed chute above each cooling section, as shown in FIGS. 7 and12. The motor causes the discharge wheels 62' and 63 to dischargegrain'when the level L reaches the level of the detector 97, as shown inFIG. 7. When this level drops below this height the motor 96 isautomatically shut .olf to stop the operation of the rotary dischargewheels 62' and 63 and allow the level of grain to build up to therequired point. When the level reaches the proper point the detectoragain startsthe motor 96 to again cause grain to be discharged. In casethe detector 97 fails to operate, there is a safety device 100 wellbelow the air lock passageway. If the level of grain falls below thispoint a horn or other signal sounds. This safety device is arranged tooperate the same as is illustrated in FIG. 10. Above the normal level Lis another safety device 101. If the level gets to this point the device101 will also act vtosound a signal or .turn on a light to prevent toohigh a level of grain. These level detectors may be of any knowncommercially available [ype I Cooling air is adapted to enter holes 65in the bottom of each cooling unit, and air also enters holes 66 communicating with ends of the air cooling ducts 57. In addition, there areopen-bottomed cooling ducts 67 which extend through each cooling sectionat right angles to the duct 66. These ducts 67 connect with openings 69in the lower portion of the air duct' 56.

Referring now to FIGS. 6, 7 and 8, the air which enters the openings 66of FIG. 7 flows out of the bottoms of the ducts 57 and rises, enteringthe bottoms of the ducts 67. An exhaust fan 75 having an outlet opening76 and driven by a suitable motor 77 is connected through ducts 78 and79 with the opening 70 to create a suction within the suction duct 56,which suction causes the cooling air to move upwardly through thedescending grain.

Referring now to FIG. 6, atmospheric air from the blowers 71 passesthrough ducts 72 into the lower ends of the vertical ducts 73. This airflows upwarly past and through burners 74 located in the lower end ofthe ducts 52 in the plenum area 51. Here the air is heated to arelatively high temperature, higher than is usually consideredpermissible in grain drying applications. After being heated by theburners the heated air enters the ducts 52 to flow upwardly therein andenter the openings 53 of FIG. 4 leading to the tiered'hot air ducts 32.

SUMMARY OF OPERATION In operation, the grain entering the hopper at thetop is distributed by the augers 21 and 22 in both directions and iscaused to fall on top of the inclined walls 26 so that part is directedin one direction and part in the opposite direction on each side of theplenum. Grain is fed in until the inclined columns are completelyfilled, as well as the side spaces 80 of FIG. 3, and there will also bea head of grain resting on the inclined walls 26 up to the level ofdetectors 84. The blowers 71 are delivering atmospheric air past theburners 74 and this air is heated to a relatively high temperature,between 300 F. and 600 F. The blowers 71 deliver the air at highvelocity and at a pressure equal to 10-20 inches of water pressure. Thisair travels upwardly in the hot air passageways 52 and enters the endopenings 53 leading to the hot air ducts 32. In each hot air duct 32 theair is divided, part flowing in the passageway 41 and part flowing inthe passageway 42. The air is then delivered in a down direction, asindicated by the arrows in FIG. 3, at high velocity and pressure throughthe inclined columns of grain. In moving the air through the columns ofgrain it takes substantial pressure, which pressure, as before stated,is equal to 10-20 inches of water pressure.

At the same time the metering wheels 48 are being rotated at arelatively slow rate, the hot air flowing in the same direction as thegrain. However, it may take 15 minutes to an hour for the grain totravel the length of the inclines 31, depending upon the speed of thedischarge meters 48, whereas the hot air is moving at high velocity,taking less than a second .to travel through the entire depth of thebeds of grain. This air can be at a relatively high temperature,depending upon the requirements of the particular products, and may beas high as 600 F. It is usually between 300600 F. The discharged dryingair flows upwardly in the central chambers 49 and then out of the topoutlet 81 through communicating opening 81' (FIG. 4).

The temperature of the air emerging from the inclined shelves throughthe perforated closure plates 47 is sensed by the temperature-responsivedevice 94. Since the temperature and pressure of the entering air arecontrolled to fixed values, the quantity of moisture removed from thegrain is a function of the length of time the grain takes to passthrough the dryer. The warm air, entering at 53, gives up heat to thegrain, warming the grain and cooling the air. As the grain warms, itgives up moisture, further cooling the air by evaporative cooling. Thetemperature-sensing device 94 is immersed in the air which emerges fromthe drying shelves 31. Thus, under running conditions, if the exit airis cooler than the temperature which has been set on thetemperature-sensing device, the grain is moving through the dryer toorapidly, and the grain metering wheels 48 should be slowed. Conversely,if the air is too warm, the grain flow rate should be increased. As analternative, a known type of temperaturesensing device may be located inthe exiting grain as at 194 (FIG. 7). Thus under running conditions ifthe grain at this region is cooler than the temperature which has beenset on the temperature-sensing device, the grain is moving through thedryer too rapidly and the grain metering wheels 48 should be slowed. Asanother alternative, the sensing device, instead of being responsive totemperature, can be any well known type which is responsive to themoisture of the exiting grain as at 294 (FIG. 7). In this situation, ifthe exiting grain is too moist, then the grain is moving through thedryer too rapidly and the grain metering wheels 48 should be slowed.

A change of speed of grain flow has almost no affect on the temperatureof the exit air for a period of time say 10 to 20 minutes, so it isdesirable to wait for approximately this time interval to determine ifthe change made was correct, insufficient, or too much. If the change inflow rate was insuflicient, additional change in the same directionshould be made. If the correction was too much, the rate should bechanged in the opposite direction.

The grain which is metered out by the metering wheels 48 fallsdownwardly in the space 49, out of the opening 50 of FIG. 3, and ontothe inclined walls 55 of FIG. 7, where it is divided, descending down ontop of the cooling ducts 57, baflles 58, 60 and 61., and eventually ontothe discharge belt 64. This action is under the control of the rotarydischarge valves 62 and 63'. As the grain descends, cooling air whichenters the spaces 65 of FIG. 7 and also the ends of the air ducts 66 issucked out of the lower ends of the ducts 66 and caused to rise throughthe descending grain in countercurrent. The cooling air is then drawninto the bottoms of the ducts 67, into the openings 69, and out of theexhaust openings 70. This, of course, is accomplished by the action ofthe exhaust fan 75 which is connected by the ducts 78 and 79 with theend opening 70 of the suction duct 56. The grain in the area betweenlevel L of FIG. 7 and the lower portion of the ducts 67 is free from theeffect of either hot air currents or cooling air. This area may,therefore, be termed a tempering area where the moisture in the kernelshas a chance to reach a state of equilibrium. This allows the grain, asit descends into the region where it is acted upon by the cooling air,to release some additional moisture to the cooling air, which releaseserves to speed up the cooling process by aiding in the evaporativecooling efi'ect. Due to this tempering area and to the counterflowcooling, there is an absence of undesriable stresscracked kernels.

With the improved dryer, higher temperatures are possible for the dryingair because the hot air is only in contact with the grain in theinclined beds for a short period of time, as the air is moving at highvelocity and at high pressure. Heretofore dryers have been cumbersomelylarge so that lower temperature air could be used to contact the grain,such as corn, at a longer period of time, and it has heretofore beencustomary to have the heated air at a temperatude of about 230 F.maximum.

By having the tiers of angular drying shelves it is possible to use asmaller installation while still permitting the use of relatively highair temperatures for a relatively short period of time. Prior art graindryers have been cumbersomely large so that lower temperature air couldbe used to contact the corn for a suificient length of time toaccomplish drying.

With the arrangement of the present invention, the air discharged fromthe ducts 32 passes uniformly through the entire body of grain on eachshelf to accomplish uniform drying, with all particles being subjectedto substantially the same amount of heat for substantially the samelength of time. Thus, there is high drying efficiency. With the presentinvention all of the drying air is exhausted at one place, through theexhaust duct 81. Thus, pollution control need be carried on at thispoint only.

While it is desirable to employ the cooler in the arrangementillustrated and heretofore described, the drying apparatus is usefulwith or without the cooling adjunct. There are users who may prefer tocool the dry product through other methods of their own selection. Thepresent invention, therefore, contemplates the use of the dryer eitherwith or without the cooling arrangement shown and described. Inaddition, the principles of the invention may be employed with only onetier of shelves 31 instead of the four tiers illustrated, two on eachside. Also, any multiple of tiers may be used.

What we claim is:

1. A dryer comprising a tier of spaced inclined shelves, each shelfhaving an upper portion and a lower portion, a heating duct of lessheight than the space between shelves extending along the upper portionof each shelf and having air .openings positioned to direct airdownwardly along the inclined shelf, means for maintaining the spacebetween each pair of shelves and over the heating duct filled with a bedof grain, means at the lower end of each bed for controlling themetering of grain from the bed, there being air discharge openings atsaid lower end for the discharge of drying air from each bed, and meansfor delivering heated air to the heating ducts at high velocity and atsufficient pressure to cause the air to travel rapidly through theinclined beds of grain to dry the latter while grain is being meteredslowly from each bed.

2. A dryer as claimed in claim 1 in which the means for deliverying theheated air to the heating ducts includes a common plenum chambercommunicating with the ends of the heating ducts.

3. A dryer as claimed in claim 1 in which there are two sets of spacedinclined tiers of shelves, the tiers of one set being inclined towardthe tiers of the other set, and in which there is a common dischargespace between the two sets of tiers through which grain metered from thebeds falls and from the upper ends of which the drying air is exhausted.

4. A dryer as claimed in claim 3 in which there is means for deliveringgrain to both tiers to maintain the grain beds filled.

5. A dryer as claimed in claim 1 in which there is means including anauger for feeding grain toward the beds to keep them filled, in whichthere is a motor for driving the auger, and in which there is means forautomatically shutting oif the motor when the grain is above apredetermined level and for starting the auger motor when the grain isbelow said level.

6. A dryer as claimed in claim 1 in which there is a level detectornormally maintained in inoperative position by grain when the level ofthe latter is above said detector, and in which there is meanscontrolled by said detector for operating a signal when the level of thegrain is below the detector.

7. A dryer as claimed in claim 1 in which the means at the lower end ofsuch grain bed isa rotary metering wheel, in which there is a variablespeed motor for driving all of the rotary metering wheels.

8. A dryer as claimed in claim 1 in which there is a cooler below thedryer, and in which there is means providing for restricted flow ofgrain discharged from the dryer into the cooler, said restricted flowmeans serving as a seal against the entrance of drying air into thecooler.

S. A dryer as claimed in claim 1 in which there is a cooler, means fordirecting dried grain from the dryer into the cooler, rotary meteringwheels for discharging dried and cooled grain from the cooler, and meansresponsive to the level of grain in the cooler for controlling theoperation of said rotary metering wheels.

10. A dryer as claimed in claim 1 in which there is drive mechanism fordriving the metering means at a selected speed, the inclined shelvesbeing at such an angle that the grain flows by gravity from each bed ata rate determined by the speed of the metering means.

11. A dryer as claimed in claim 10 in which the metering means comprisesa metering paddle wheel for each bed and in which the rate of dischargeis determined by the rotational speed of said wheels.

12. A dryer as claimed in claim 1 in which there is a cooler below thedryer, means for directing dried grain from the dryer to the cooler,means for discharging dried and cooled grain from the cooler, and meansfor causing cooling air to flow in counter current to the descendinggrain in the cooler.

13. A dryer as claimed in claim 1 in which there is a cooler below thedryer, means for directing dried grain from the dryer to the cooler,means for discharging dried and cooled grain from the cooler, means forcausing cooling air to flow from the lower portion of the coolerupwardly in counter current to the descending grain in the cooler, andmeans for discharging said cooling air at a location short of the top ofthe cooler whereby there is a tempering area thereabove in which thegrain in free of the effects of both cooling air and drying air.

14. A dryer as claimed in claim 1 in which the angle of the shelves isbetween 40 and 60 degrees from the horizontal.

15. A dryer as claimed in claim 1 in which the ratio between thedistance between shelves and the mean depth of each bed of grain is inthe range between 1/l.5 and l/ 8.

16. A dryer as claimed in claim 1 in which the ratio between the heightof the hot air duct and the distance between shelves is in the rangebetween 1/2 and 9/10.

17. A dryer as claimed in claim 1 in which the ratio between thedistance between shelves and the mean depth of each bed of grain is inthe range between 1/ 1.5 and 1/8, and in which the ratio between theheight of the hot air duct and the distance between shelves is in therange between 1/ 2 and 9/ 10.

18. A dryer as claimed in claim 1 in which the angle of the shelves isbetween 40 and 60 degrees from the horizontal, in which the ratiobetween the distance be tween shelves and the mean depth of each bed ofgrain is in the range between 1/ 1.5 and 1/8, and in which the ratiobetween the height of the hot air duct and the dis- References CitedUNITED STATES PATENTS 2,060,581 11/1936 Laessig 3465UX 2,759,274 8/1956Jonsson 3 4-65X 3,274,701 9/1966 Niemitz 34168X 10 CARROLL B. DORITY,JR., Primary Examiner US. Cl. XJR. 34-65, 67, 168 3

